UV-Vis Optical Spectra Modeling for Analyzing Filter Cake Breaker Stability Using First-Principles Density Functional Theory

Abstract This paper investigates the photophysical stability and electronic properties of EDTA and its complexes with Ca, Fe, and Zn, evaluating their performance as filter cake breaker agents under simulated downhole conditions. The focus is on quantifying stability via real-time time-dependent DFT (TDDFT)-derived lifetimes, dipole behaviour, and absorption spectra. Ground-state and excited-state properties were calculated using density functional theory (DFT) and TDDFT in the GPAW code. Each system, EDTA, EDTA+Ca+H2O, EDTA+Fe+H2O, and EDTA+Zn+H2O, was optimized, followed by SCF and TDDFT simulations. Optical absorption spectra were extracted from dipole moment time-series, with Gaussian and Lorentzian broadening, and fitted exponential decay curves provided radiative lifetimes. Directional polarizabilities, thermal dipole deviations (at 300K), and transition densities were analyzed. Metal coordination substantially enhanced EDTA stability, as reflected in HOMO–LUMO gaps (EDTA: 3.60 eV; EDTA+Ca+H2O: 1.56 eV; EDTA+Fe+H2O: 2.44 eV; EDTA+Zn+H2O: 3.43 eV) and dipole lifetimes (EDTA: 643 fs; Ca: 2092 fs; Fe: 524 fs; Zn: 877 fs). EDTA+Ca+H2O showed the highest filter cake stability, with the longest radiative lifetime and moderate thermal dipole deviation (std = 0.256 at 300 K). TDDFT spectra revealed blue-shifts and greater oscillator strengths for metal complexes. Directional polarizability analysis identified αxx as the dominant response, peaking near 1.66 eV for all complexes. Transition density maps confirmed greater electronic coherence and persistent excitation in metal-EDTA systems, especially for Ca and Zn. These results indicate that metal-complexed EDTA, particularly the Ca system, exhibits superior electronic and photophysical stability for filter cake decomposition. This study is the first to benchmark EDTA and its metal complexes for filter cake breaker performance using a unified first-principles TDDFT framework. The combination of optical spectra, lifetimes, and thermal response provides new predictive tools for downhole chemical design, advancing both fundamental understanding and practical application of chelate-based filter cake remediation.